Aiming for zero imports I didn't write.
Optimised for readability (I am not a miser about newlines like actual haskellers). Actually I guess that's not true, since I'm a lazy bastard and never say my types.
runhaskell is often unbearably slow, but most of these run in <2s with ghc -O2.
I always solve the general case, but am happy to add hacky and approximate shortcuts.